Coupling of arylamine with coordinated arylazopyrimidine in platinum(II) complexes. Single crystal X-ray structure, spectra and electrochemistry

摘要

2-(Arylazo)pyrimidine (p-R-C6H4-N=N-C4H3N2, aapm, R=H (papm, 3a), Me (tapm, 3b), Cl (Clpapm, 3c)) are N,N'-chelating ligands. Platinum(II) complexes, Pt(aapm)Cl-2 (4) have been synthesized by the reaction of K2PtCl4 and aapm in MeCN-water under refluxing condition. The reaction of Pt(aapm)Cl-2 with ArNH2 in MeCN has synthesized C-N coupled product, Pt(aapm-N-Ar)Cl (5-10). The single crystal X-ray structure determination of one of the compounds has suggested the coupling of ArNH2 at ortho-C-H of the pendant aryl part of aapm in the chelated complex. The stereochemistry and the bonding are described by H-1 NMR data. The solution electronic spectra of Pt(aapm-N-Ar)Cl exhibit multiple transition at Vis-NIR region (500-1250 nm) which are absent in Pt(aapm)Cl-2. Cyclic voltammograms show two quasireversible azo reductions of Pt(aapm)Cl-2; Pt(aapm-N-Ar)Cl exhibit four successive redox couples, one of them (positive to SCE) is oxidative in nature and other (negative to SCE) are ligand reductions. (C) 2005 Elsevier Ltd. All rights reserved.